Study of exchange bias effect in bilayers based on La2/3Ca1/3MnO3 and BiFeO3

BiFeO₃ (BFO) is an interesting material due to the coexistence of magnetic and ferroelectric order at room temperature. Moreover, mixed manganese perovskite oxides like ferromagnetic La_2/3Ca_1/3MnO₃ (LCMO-F) present remarkable properties, like colossal magnetoresistance and non-volatile memory. Bilayers of BFO/LCMO-F and LCMO-F/BFO were grown on (100) SrTiO₃ (STO) substrates. LCMO-F films were deposited by DC sputtering and BFO by RF magnetron sputtering technique at high-oxygen pressures. Samples were structurally characterized by x-ray diffractometry. Electrical properties were evaluated by resistivity measurements as function of temperature, showing how the transition temperature of manganite is affected by the presence of the BFO layer. Magnetic characterizations were carried out by magnetization measurements as function of temperature and magnetic field. BFO/LCMO-F/STO bilayer showed a higher Curie temperature than LCMO-F layers grown by similar parameters. Magnetic hysteresis curves for LCMO-F/BFO/STO bilayers gave us indication of the existence of exchange bias effect with a Hex of 200 Oe after field cooling at 1 T; we can also conclude that this bilayer configuration offers posibilities to obtain bilayers exhibiting this polarization effect.